Field of the Invention
The present invention is broadly concerned with improved, high security switch apparatus, which can be used as a part of an alarm system responsive to unauthorized opening of a door or the like of a protected structure. More particularly, the invention is concerned with such apparatus which makes use of a ball-type magnetic switch assembly having an elongated housing and a magnetically shiftable ball therein. The ball traverses a path of travel between respective switch states which is oriented substantially horizontally, in order to prevent defeat of the alarm system through use of a defeat magnet located on the exterior of the protected structure.
Description of the Prior Art
Prior art security alarm systems often make use of magnetic switches attached to doors and windows and integrated with the system for detecting unauthorized openings. One common type of magnetic switch used in these situations is a so-called reed switch. It has been found that reed switches are subject to unauthorized manipulation through use of an external magnet. Specifically, an intruder can hold a relatively strong magnet adjacent the reed switch which will then be operated (to either open or close depending on the control scheme). With this accomplished, an intruder can open the door or window without triggering the alarm system.
A number of magnetic switches have been proposed in the past to overcome the inherent deficiencies of reed switches. U.S. Pat. Nos. 5,332,992, 5,530,428, 5,673,021, 5,880,659, 5,977,873, 6,087,936, 6,506,987, 6,603,378, 7,023,308, 7,291,794, 7,825,801, 8,228,191, and 8,314,698 describe switches of this type. These switches typically include a pair of spaced apart switch elements with a shiftable body (e.g., a spherical ball) vertically movable within an upright housing between a first position where the ball is in simultaneous contact with both elements and a second position out of such simultaneous contact. An alarm circuit is operatively coupled with the switch elements so as to detect movement of the body. These switches represent a very significant advance in the art. The Magnasphere Corporation of Waukesha, Wis., has commercialized a series of magnetic switches of this type.
U.S. Pat. No. 8,648,720 describes a magnetic ball switch which is specifically designed for protecting an internal door or the like within a building or other structure, e.g., a high-security coding room. The '720 patent describes a switch assembly which is suitable for mounting on an internal door frame and door, and protects against an attempted illegal entry making use of a defeat magnet placed adjacent the internally mounted switch assembly. To this end, the switch assembly provides a magnetic ball switch which is oriented at an oblique angle relative to the horizontal so that attempted opening via an internal defeat magnet will activate an alarm. However, the switch assembly of the '720 patent is not appropriate for protecting an exterior door or window which would provide a potential entryway from the exterior of the building or structure to the interior thereof.